During the combustion cycle of conventional internal combustion engines, some combustion gases may leak past the piston rings of the cylinder and into the crankcase. These leaked gases are often referred to as blow-by gases. Crankcase ventilation (“CV”) systems are employed to vent the blow-by gases from the crankcase. Some CV systems are open loop systems, meaning the blow-by gases are vented to the ambient environment. Other CV systems are closed loop systems, meaning the blow-by gases are returned to the engine for combustion.
Many CV systems include a crankcase ventilation filter that allows the blow-by gases to be swept out of the crankcase (e.g., out of a road draft tube, into the engine intake, etc.). The crankcase ventilation filter may be a coalescing filter, a ventilation rotating filter, a coalescer, an inertial separator or the like. The crankcase ventilation filter may assist in treating the blow-by gases to reduce environmental impact of the internal combustion engine. In some situations, oil contained in the crankcase may backtrack into the crankcase ventilation filter. Backtracked oil may damage the CV system and/or the engine if it enters and remains in the crankcase ventilation filter. Accordingly, the crankcase ventilation filter may include a drain chamber to route any backtracked oil back to the engine or crankcase. However, in some engines, oil contained in the crankcase is at a higher pressure than the oil in the crankcase ventilation filter drain. Thus, the oil in the crankcase ventilation filter drain may need to be pumped back into the engine or crankcase to overcome the pressure differential.
Some CV systems utilize an oil jet pump to help drain separated oil in the drain chamber of the crankcase ventilation filter back to the crankcase. Pressurized oil is forced through a nozzle, which creates a high-velocity stream of engine oil that is directed towards a mixing bore of the oil driven jet-pump in the CV system. The mixing bore is arranged adjacent to the crankcase ventilation filter drain along a conduit routing oil back to the engine or crankcase. The high-velocity stream of oil leaving the nozzle and entering the mixing bore creates shear forces on the oil in the drain chamber. The shear forces draw the oil from the crankcase ventilation filter drain into the conduit routing oil back to the engine or crankcase thereby creating a pumping effect.
However, under cold engine conditions, the oil may be too viscous to form the required high-velocity stream that creates the necessary shear forces to draw oil from the crankcase ventilation filter drain to the conduit routing the oil back to the engine or crankcase. The high viscosity may be the result of the oil's low temperature caused by a cold engine condition. Additionally, under cold engine conditions, the pressurized oil may flow into the crankcase ventilation filter drain and potentially damage the crankcase ventilation filter and or cause oil loss due to increased oil consumption.